Hm...These are all 'indie pop' at one point or another. Pavement, Pixies, Flaming Lips, and Sonic Youth are probably more leaning towards alternative rock or noise-wave. Modest Mouse and Death Cab I'd say are more indie rock.

Yeah, I try to think of it like this; does this sound poppish or more like rock. I kinda of have my own genre for a few bands that I could consider indie, garage rock,- the White Stripes, Strokes, and Black Keys. I think Death Cab if Indie Pop; Plans is pretty poppy. PuddlesPuddles... I like how you phrase it, most bands change, some of their albums are more poppy than otheres.